Probe card assembly and kit

ABSTRACT

In a probe card assembly, a series of probe elements can be arrayed on a silicon space transformer. The silicon space transformer can be fabricated with an array of primary contacts in a very tight pitch, comparable to the pitch of a semiconductor device. One preferred primary contact is a resilient spring contact. Conductive elements in the space transformer are routed to second contacts at a more relaxed pitch. In one preferred embodiment, the second contacts are suitable for directly attaching a ribbon cable, which in turn can be connected to provide selective connection to each primary contact. The silicon space transformer is mounted in a fixture that provides for resilient connection to a wafer or device to be tested. This fixture can be adjusted to planarize the primary contacts with the plane of a support probe card board.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 10/889,334, filed Jul. 12, 2004 (now U.S. Pat. No. 7,061,257),which is a continuation of U.S. patent application Ser. No. 10/458,875,filed Jun. 10, 2003 (now U.S. Pat. No. 6,838,893), which is acontinuation of U.S. patent application Ser. No. 09/042,606, filed Mar.16, 1998, which claims the benefit of U.S. Provisional PatentApplication No. 60/040,983 filed 17 Mar. 1997 by Khandros and Sporck,

said U.S. patent application Ser. No. 09/042,606 is acontinuation-in-part of commonly-owned, U.S. patent application Ser. No.08/554,902 filed 9 Nov. 1995 by Eldridge, Grube, Khandros and Mathieu(now U.S. Pat. No. 5,974,662),

which is a continuation-in-part of commonly-owned U.S. patentapplication Ser. No. 08/452,255 (hereinafter “PARENT CASE”), filed 26May 1995 by Eldridge, Grube, Khandros and Mathieu (now U.S. Pat. No.6,336,269),

which is a continuation-in-part of commonly-owned U.S. patentapplication Ser. No. 08/340,144 filed 15 Nov. 1994 by Khandros andMathieu (now U.S. Pat. No. 5,917,707),

which is a continuation-in-part of commonly-owned U.S. patentapplication Ser. No. 08/152,812, filed Nov. 16, 1993 by Khandros(status: issued as U.S. Pat. No. 5,476,211).

TECHNICAL FIELD OF THE INVENTION

The invention relates to an apparatus and associated techniques formaking pressure connections between electronic components with resilient(spring) contact elements, such as for performing test and burn-inprocedures on semiconductor devices prior to their packaging, preferablyprior to the individual semiconductor devices being singulated from asemiconductor wafer.

BACKGROUND OF THE INVENTION

The aforementioned commonly-owned, copending U.S. patent applicationSer. No. 08/554,902 filed 9 Nov. 1995 and its corresponding PCT PatentApplication No. PCT/US95/14844 filed 13 Nov. 1995 (WO96/15458, published23 May 1996), both by ELDRIDGE, GRUBE, KHANDROS and MATHIEU, disclose aprobe card assembly. As illustrated, for example, in FIG. 5 therein, theprobe card assembly (500) includes a probe card (502), a spacetransformer (506) having resilient contact structures (probe elements524) mounted directly to and extending from terminals (522) on a surfacethereof, and an interposer (504) disposed between the space transformer(506) and the probe card (502). The space transformer (506) andinterposer (504) are “stacked up” so that the orientation of the spacetransformer (506), hence the orientation of the tips of the probeelements (524), can be adjusted without changing the orientation of theprobe card. Suitable mechanisms (532, 536, 538, 546) for adjusting theorientation of the space transformer (506), and for determining whatadjustments to make, are disclosed therein. Multiple die sites on asemiconductor wafer (508) are readily probed using the disclosedtechniques, and the probe elements (524) can be arranged to optimizeprobing of an entire wafer (508). As shown, for example, in FIG. 2Atherein, the resilient contact structures or probe elements (524) aresuitably (but not limited to) composite interconnections elements (200)having a relatively soft core (206) overcoated by a relatively hardshell (218,220).

Generally, the present invention obviates the need for using a spacetransformer (e.g., 506) and an interposer (504) in a probe card assemblythat may be adjusted in a manner similar to that described in theabove-referenced patent applications.

Among the problems associated with using a space transformer componentin a probe card assembly is that of matching the coefficients of thermalexpansion of the space transformer to that of the wafer under test(WUT). Furthermore, in some instances, depending on the materials (e.g.,ceramic layers, terminals, etc.) and processes employed in themanufacture of the space transformer component, it can be difficult toachieve a reliable mechanical connection between free-standing resilient(spring) contact elements mounted to the terminals of the spacetransformer under the stresses encountered when making repeated pressureconnections to terminals of other electronic components, such as wouldbe encountered when probing a sequence of WUTs or a series of die siteson a one or more WUTs.

The use of a separate interposer component in a probe card assembly canalso be undesirable. Simply stated, it is one more component that mustsuccessfully be yielded and incorporated into the probe card assembly.

The present invention advantageously employs, but does not requireapplicant's own free-standing, resilient, “composite” interconnectionelements, which are described in one or more of the above referencedcommonly-owned patents and patent applications.

Commonly-owned U.S. patent application Ser. No. 08/152,812 filed 16 Nov.1993 (now U.S. Pat. No. 4,576,211), and its counterpart commonly-ownedcopending “divisional” U.S. patent application Ser. No. 08/457,479 filed1 Jun. 1995 (status: pending) and Ser. No. 08/570,230 filed 11 Dec. 1995(status: pending), all by KHANDROS, disclose methods for makingresilient (spring) interconnection elements for microelectronicsapplications involving mounting an end of a flexible elongate coreelement (e.g., wire “stem” or “skeleton”) to a terminal on an electroniccomponent coating the flexible core element and adjacent surface of theterminal with a “shell” of one or more materials having a predeterminedcombination of thickness, yield strength and elastic modulus to ensurepredetermined force-to-deflection characteristics of the resultingspring contacts. Exemplary materials for the core element include gold.Exemplary materials for the coating include nickel and its alloys. Theresulting spring contact element is suitably used to effect pressure, ordemountable, connections between two or more electronic components,including semiconductor devices, and is well-suited to use as a probeelement of a probe card assembly.

Commonly-owned, copending U.S. patent application Ser. No. 08/340,144filed 15 Nov. 1994 and its corresponding PCT Patent Application No.PCT/US94/13373 filed 16 Nov. 1994 (WO95/14314, published 26 May 1995),both by KHANDROS and MATHIEU, disclose a number of applications for theaforementioned spring contact elements, and also discloses techniquesfor fabricating contact pads at the ends of the spring contact elements.For example, in FIG. 14 thereof, a plurality of negative projections orholes, which may be in the form of inverted pyramids ending in apexes,are formed in the surface of a sacrificial layer (substrate). Theseholes are then filled with a contact structure comprising layers ofmaterial such as gold or rhodium and nickel. A flexible elongate elementis mounted to the resulting contact structure and can be overcoated inthe manner described hereinabove. In a final step, the sacrificialsubstrate is removed. The resulting spring contact has a contact padhaving controlled geometry (e.g., sharp points) at its free end.

Commonly-owned, copending U.S. patent application Ser. No. 08/452,255filed 26 May 1995 and its corresponding PCT Patent Application No.PCT/US95/14909 filed 13 Nov. 1995 (WO96/17278, published 6 Jun. 1996),both by ELDRIDGE, GRUBE, KHANDROS and MATHIEU, disclose additionaltechniques and metallurgies for fabricating contact tip structures onsacrificial substrates, as well as techniques for transferring aplurality of spring contact elements mounted thereto, en masse, toterminals of an electronic component (see, e.g., FIGS. 11A-11F and12A-12C therein). These patent applications also disclose techniques forfabricating free-standing “composite” resilient (spring) contactelements directly on silicon substrates, including on active devices.

Commonly-owned, copending U.S. Provisional Patent Application No.60/005,189 filed 17 May 1996 and its corresponding PCT PatentApplication No. PCT/US96/08107 filed 24 May 1996 (WO96/37332, published28 Nov. 1996), both by ELDRIDGE, KHANDROS, and MATHIEU, disclosestechniques whereby a plurality of contact tip structures (see, e.g, #620in FIG. 6B therein) are joined to a corresponding plurality of elongatecontact elements (see, e.g., #632 of FIG. 6D therein) which are alreadymounted to an electronic component (#630). This patent application alsodiscloses, for example in FIGS. 7A-7E therein, techniques forfabricating “elongate” contact tip structures in the form ofcantilevers. The cantilever tip structures can be tapered, between oneend thereof and an opposite end thereof. The cantilever tip structuresof this patent application are suitable for mounting to already-existing(i.e., previously fabricated) raised interconnection elements (see,e.g., #730 in FIG. 7F) extending (e.g., free-standing) fromcorresponding terminals of an electronic component (see. e.g., #734 inFIG. 7F).

Commonly-owned, copending U.S. Provisional Patent Application No.60/024,555 filed 26 Aug. 1996, by ELDRIDGE, KHANDROS and MATHIEU,discloses, for example at FIGS. 2A-2C thereof, a technique whereby aplurality of elongate tip structures having different lengths than oneanother can be arranged so that their outer ends are disposed at agreater pitch than their inner ends. Their inner, “contact” ends may becollinear with one another, for effecting connections to electroniccomponents having terminals disposed along a line, such as a centerlineof the component.

The present invention addresses and is particularly well-suited tomaking interconnections to modern microelectronic devices having theirterminals (bond pads) disposed at a fine-pitch. As used herein, the term“fine-pitch” refers to microelectronic devices that have their terminalsdisposed at a spacing of less than 5 mils, such as 2.5 mils or 65

m.

Individual semiconductor (integrated circuit) devices (dies) aretypically produced by creating several identical devices on asemiconductor wafer, using know techniques of photolithography,deposition, and the like. Generally, these processes are intended tocreate a plurality of fully-functional integrated circuit devices, priorto singulating (severing) the individual dies from the semiconductorwafer. In practice, however, certain physical defects in the waferitself and certain defects in the processing of the wafer inevitablylead to some of the dies being “good” (fully-functional) and some of thedies being “bad” (non-functional).

It is generally desirable to be able to identify which of the pluralityof dies on a wafer are good dies prior to their packaging, andpreferably prior to their being singulated from the wafer. To this end,a wafer “tester” or “prober” may advantageously be employed to make aplurality of discrete pressure connections to a like plurality ofdiscrete connection pads (bond pads) on the dies. In this manner, thesemiconductor dies can be tested and exercised, prior to singulating thedies from the wafer.

A conventional component of a wafer tester is a “probe card” to which aplurality of probe elements are connected—tips of the probe elementseffecting the pressure connections to the respective bond pads of thesemiconductor dies.

Certain difficulties are inherent in any technique for probingsemiconductor dies. For example, modern integrated circuits include manythousands of transistor elements requiring many hundreds of bond padsdisposed in close proximity to one another (e.g., 5 milscenter-to-center). Moreover, the layout of the bond pads need not belimited to single rows of bond pads disposed close to the peripheraledges of the die (See, e.g., U.S. Pat. No. 5,453,583).

To effect reliable pressure connections between the probe elements andthe semiconductor die one must be concerned with several parametersincluding, but not limited to: alignment, probe force, overdrive,contact force, balanced contact force, scrub, contact resistance, andplanarization. A general discussion of these parameters may be found inU.S. Pat. No. 4,837,622, entitled HIGH DENSITY PROBE CARD, incorporatedby reference herein, which discloses a high density epoxy ring probecard including a unitary printed circuit board having a central openingadapted to receive a preformed epoxy ring array of probe elements.

Generally, prior art probe card assemblies include a plurality oftungsten needles extending as cantilevers from a surface of a probecard. The tungsten needles may be mounted in any suitable manner to theprobe card, such as by the intermediary of an epoxy ring, as discussedhereinabove. Generally, in any case, the needles are wired to terminalsof the probe card through the intermediary of a separate and distinctwire connecting the needles to the terminals of the probe card.

Probe cards are typically formed as circular rings, with hundreds ofprobe elements (needles) extending from an inner periphery of the ring(and wired to terminals of the probe card). Circuit modules, andconductive traces (lines) of preferably equal length, are associatedwith each of the probe elements. This ring-shape layout makes itdifficult, and in some cases impossible, to probe a plurality ofunsingulated semiconductor dies (multiple sites) on a wafer, especiallywhen the bond pads of each semiconductor die are arranged in other thantwo linear arrays along two opposite edges of the semiconductor die.

Wafer testers may alternately employ a probe membrane having a centralcontact bump area, as is discussed in U.S. Pat. No. 5,422,574, entitledLARGE SCALE PROTRUSION MEMBRANE FOR SEMICONDUCTOR DEVICES UNDER TESTWITH VERY HIGH PIN COUNTS, incorporated by reference herein. As noted inthis patent, “A test system typically comprises a test controller forexecuting and controlling a series of test programs, a wafer dispensingsystem for mechanically handling and positioning wafers in preparationfor testing and a probe card for maintaining an accurate mechanicalcontact with the device-under-test (DUT).” (column 1, lines 41-46).

Additional references, incorporated by reference herein, as indicativeof the state of the art in testing semiconductor devices, include U.S.Pat. No. 5,442,282 (TESTING AND EXERCISING INDIVIDUAL UNSINGULATED DIESON A WAFER); U.S. Pat. No. 5,382,898 (HIGH DENSITY PROBE CARD FORTESTING ELECTRICAL CIRCUITS); U.S. Pat. No. 5,378,982 TEST PROBE FORPANEL HAVING AN OVERLYING PROTECTIVE MEMBER ADJACENT PANEL CONTACTS);U.S. Pat. No. 5,339,027 (RIGID-FLEX CIRCUITS WITH RAISED FEATURES AS ICTEST PROBES); U.S. Pat. No. 5,180,977 (MEMBRANE PROBE CONTACT BUMPCOMPLIANCY SYSTEM); U.S. Pat. No. 5,066,907 (PROBE SYSTEM FOR DEVICE ANDCIRCUIT TESTING); U.S. Pat. No. 4,757,256 (HIGH DENSITY PROBE CARD);U.S. Pat. No. 4,161,692 (PROBE DEVICE FOR INTEGRATED CIRCUIT WAFERS);and U.S. Pat. No. 3,990,689 (ADJUSTABLE HOLDER ASSEMBLY FOR POSITIONINGA VACUUM CHUCK).

Generally, interconnections between electronic components can beclassified into the two broad categories of “relatively permanent” and“readily demountable”.

An example of a “relatively permanent” connection is a solder joint.Once two components are soldered to one another, a process ofunsoldering must be used to separate the components. A wire bond isanother example of a “relatively permanent” connection.

An example of a “readily demountable” connection is rigid pins of oneelectronic component being received by resilient socket elements ofanother electronic component. The socket elements exert a contact force(pressure) on the pins in an amount sufficient to ensure a reliableelectrical connection therebetween.

Interconnection elements intended to make pressure contact withterminals of an electronic component are referred to herein as “springs”or “spring elements”. Generally, a certain minimum contact force isdesired to effect reliable pressure contact to electronic components(e.g., to terminals on electronic components). For example, a contact(load) force of approximately 15 grams (including as little as 2 gramsor less and as much as 150 grams or more, per contact) may be desired toensure that a reliable electrical connection is made to a terminal of anelectronic component which may be contaminated with films on itssurface, or which has corrosion or oxidation products on its surface.The minimum contact force required of each spring demands either thatthe yield strength of the spring material or that the size of the springelement are increased. As a general proposition, the higher the yieldstrength of a material, the more difficult it will be to work with(e.g., punch, bend, etc.). And the desire to make springs smalleressentially rules out making them larger in cross-section.

Probe elements are a class of spring elements of particular relevance tothe present invention. Prior art probe elements are commonly fabricatedfrom tungsten, a relatively hard (high yield strength) material. When itis desired to mount such relatively hard materials to terminals of anelectronic component, relatively “hostile” (e.g., high temperature)processes such as brazing are required. Such “hostile” processes aregenerally not desirable (and often not feasible) in the context ofcertain relatively “fragile” electronic components such as semiconductordevices. In contrast thereto, wire bonding is an example of a relatively“friendly” processes which is much less potentially damaging to fragileelectronic components than brazing. Soldering is another example of arelatively “friendly” process. However, both solder and gold arerelatively soft (low yield strength) materials which will not functionwell as spring elements.

A subtle problem associated with interconnection elements includingspring contact elements, is that, often, the terminals of an electroniccomponent are not perfectly coplanar. Interconnection elements lackingin some mechanism incorporated therewith for accommodating these“tolerances” (gross non-planarities) will be hard pressed to makeconsistent contact pressure contact with the terminals of the electroniccomponent.

The following U.S. Patents, incorporated by reference herein, are citedas being of general interest vis-a-vis making connections, particularlypressure connections, to electronic components: U.S. Pat. No. 5,386,344(FLEX CIRCUIT CARD ELASTOMERIC CABLE CONNECTOR ASSEMBLY); U.S. Pat. No.5,336,380 (SPRING BIASED TAPERED CONTACT ELEMENTS FOR ELECTRICALCONNECTORS AND INTEGRATED CIRCUIT PACKAGES); U.S. Pat. No. 5,317,479(PLATED COMPLIANT LEAD); U.S. Pat. No. 5,086,337 (CONNECTING STRUCTUREOF ELECTRONIC PART AND ELECTRONIC DEVICE USING THE STRUCTURE); U.S. Pat.No. 5,067,007 (SEMICONDUCTOR DEVICE HAVING LEADS FOR MOUNTING TO ASURFACE OF A PRINTED CIRCUIT BOARD); U.S. Pat. No. 4,989,069(SEMICONDUCTOR PACKAGE HAVING LEADS THAT BREAK-AWAY FROM SUPPORTS); U.S.Pat. No. 4,893,172 (CONNECTING STRUCTURE FOR ELECTRONIC PART AND METHODOF MANUFACTURING THE SAME); U.S. Pat. No. 4,793,814 (ELECTRICAL CIRCUITBOARD INTERCONNECT); U.S. Pat. No. 4,777,564 (LEADFORM FOR USE WITHSURFACE MOUNTED COMPONENTS); U.S. Pat. No. 4,764,848 (SURFACE MOUNTEDARRAY STRAIN RELIEF DEVICE); U.S. Pat. No. 4,667,219 (SEMICONDUCTOR CHIPINTERFACE); U.S. Pat. No. 4,642,889 (COMPLIANT INTERCONNECTION ANDMETHOD THEREFOR); U.S. Pat. No. 4,330,165 (PRESS-CONTACT TYPEINTERCONNECTORS); U.S. Pat. No. 4,295,700 (INTERCONNECTORS); U.S. Pat.No. 4,067,104 (METHOD OF FABRICATING AN ARRAY OF FLEXIBLE METALLICINTERCONNECTS FOR COUPLING MICROELECTRONICS COMPONENTS); U.S. Pat. No.3,795,037 (ELECTRICAL CONNECTOR DEVICES); U.S. Pat. No. 3,616,532(MULTILAYER PRINTED CIRCUIT ELECTRICAL INTERCONNECTION DEVICE); and U.S.Pat. No. 3,509,270 (INTERCONNECTION FOR PRINTED CIRCUITS AND METHOD OFMAKING SAME).

BRIEF DESCRIPTION (SUMMARY) OF THE INVENTION

It is an object of the present invention to provide an improved probecard assembly.

It is an object of the present invention to provide a technique forprobing semiconductor devices, particularly while they are resident on asemiconductor wafer.

It is another object of the present invention to provide a technique forprobing semiconductor devices that allows the tips of the probe elementsto be oriented without changing the position of the probe card.

According to the invention, a probe card assembly includes:

T a probe card component such as a printed circuit board (PCB);

T an interconnection substrate such as a silicon substrate or wafersupported above a surface of the probe card;

T a plurality of resilient (spring) contact (probe) elements mounted toand extending from a first plurality of terminals (e.g., bond pads) onthe interconnection substrate;

T means for making electrical connections to the probe elements via thesilicon substrate, such as a second plurality of terminals on thesilicon substrate which can be connected to with a flexible (ribbon)cable; and

T means for adjusting the orientation of the interconnection substraterelative to the probe card such as mounting plates and differentialscrews or electrical actuators.

Together, the interconnection substrate and probe elements comprise a“probe card insert” which can be manufactured and sold as a unit forincorporation by others into a probe card assembly.

The probe card component, probe card insert, ribbon cable and means foradjusting the orientation of the interconnection substrate can bemanufactured and sold as a kit, for assembly by others into a completeprobe card assembly.

Generally, the silicon space transformer component permits a pluralityof resilient contact structures extending from its top surface to makecontact with terminals of an electronic component (i.e., bond pads onsemiconductor devices) at a relatively fine pitch (spacing), whileconnections to the space transformer (i.e., to the bond pads or,alternatively, resilient contact structures) on its bottom surface areeffected at a relatively coarser pitch.

According to an aspect of the invention, the space transformer andinterposer components of the probe card assembly may be provided as a“kit”, adapted for use with a probe card. Optionally, the mechanism foradjusting the orientation of the space transformer can be included inthe “kit”.

According to an aspect of the invention, the resilient contactstructures (probe elements) extending from the top surface of thesilicon space transformer component may (or may not) be “compositeinterconnection elements” (defined hereinbelow).

According to an aspect of the invention, the resilient contactstructures extending from the top and bottom surfaces of the interposercomponent are “composite interconnection elements” (definedhereinbelow).

Other objects, features and advantages of the invention will becomeapparent in light of the following description thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Reference will be made in detail to preferred embodiments of theinvention, examples of which are illustrated in the accompanyingdrawings. The drawings are intended to be illustrative, not limiting.Although the invention will be described in the context of thesepreferred embodiments, it should be understood that it is not intendedto limit the spirit and scope of the invention to these particularembodiments.

Certain elements in selected ones of the drawings are illustratednot-to-scale, for illustrative clarity. Often, similar elementsthroughout the drawings are referred to by similar reference numeralsFor example, the element 199 may be similar in many respects to theelement 299 in another figure. Also, often, similar elements arereferred to with similar numbers in a single drawing. For example, aplurality of elements 199 may be referred to as 199 a, 199 b, 199 c,etc.

FIG. 1 is an exploded view, partially in cross-section, of a probe cardassembly such as is disclosed in the aforementioned U.S. patentapplication Ser. No. 08/554,902 and its counterpart PCT/US95/14844, andillustrates certain techniques which are relevant to the presentinvention.

FIG. 2 is a view, partially in cross-section, and partially-schematic,of a probe card assembly similar to the probe card assembly illustratedin FIG. 1 being aligned for use in testing semiconductor wafers, such asis disclosed in the aforemetioned U.S. patent application Ser. No.08/554,902 and its counterpart PCT/US95/14844, and illustrates certaintechniques which are relevant to the present invention.

FIG. 3 is a view, partially in cross-section, and partially-schematic,of a technique for automatically adjusting the orientation of the spacetransformer component, such as is disclosed in the aforemetioned U.S.patent application Ser. No. 08/554,902 and its counterpartPCT/US95/14844, and illustrates certain techniques which are relevant tothe present invention.

FIG. 4 is a perspective view of a probe card insert, according to theinvention.

FIG. 4A is a side schematic view of a probe card assembly employing theprobe card insert of FIG. 4, according to the invention.

FIG. 4B is an exploded side view, partially in cross-section, of theprobe card assembly of FIG. 4A, showing means for adjusting theorientation of the probe card insert of FIG. 4 relative to the probecard component, according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

This patent application is directed to probe card assemblies, componentsthereof, and methods of using same. As will be evident from thedescription that follows, the use of resilient (spring) contactstructures to effect pressure connections to terminals of an electroniccomponent is essential. The resilient contact structures are suitably(but not necessarily) implemented as “composite interconnectionelements”, such as have been described in the disclosure of theaforementioned U.S. patent application Ser. No. 08/452,255 (“PARENTCASE”), incorporated by reference herein.

According to an aspect of the invention, the probe elements (resilientcontact structures extending from the top surface of the spacetransformer component) are preferably formed as “compositeinterconnection elements” which are fabricated directly upon theterminals of the space transformer component of the probe card assembly.The “composite” (multilayer) interconnection element is fabricated bymounting an elongate element (“core”) to an electronic component,shaping the core to have a spring shape, and overcoating the core toenhance the physical (e.g., spring) characteristics of the resultingcomposite interconnection element and/or to securely anchor theresulting composite interconnection element to the electronic component.The resilient contact structures of the interposer component may also beformed as composite interconnection elements.

The use of the term “composite”, throughout the description set forthherein, is consistent with a ‘generic’ meaning of the term (e.g., formedof two or more elements), and is not to be confused with any usage ofthe term “composite” in other fields of endeavor, for example, as it maybe applied to materials such as glass, carbon or other fibers supportedin a matrix of resin or the like.

As used herein, the term “spring shape” refers to virtually any shape ofan elongate element which will exhibit elastic (restorative) movement ofan end (tip) of the elongate element with respect to a force applied tothe tip. This includes elongate elements shaped to have one or morebends, as well as substantially straight elongate elements.

As used herein, the terms “contact area”, “terminal”, “pad”, and thelike refer to any conductive area on any electronic component to whichan interconnection element is mounted or makes contact.

In an embodiment of the invention, the probe elements are compositeinterconnection elements comprising a core of a “soft” material having arelatively low yield strength which is overcoated with a “hard” materialhaving a relatively high yield strength. For example, a soft materialsuch as a gold wire is attached (e.g., by wire bonding) to a bond pad ofa semiconductor device and is overcoated (e.g., by electrochemicalplating) with a hard material such nickel and its alloys.

Vis-a-vis overcoating the core, single and multi-layer overcoatings,“rough” overcoatings having microprotrusions (see also FIGS. 5C and 5Dof the PARENT CASE), and overcoatings extending the entire length of oronly a portion of the length of the core, are described. In the lattercase, the tip of the core may suitably be exposed for making contact toan electronic component (see also FIG. 5B of the PARENT CASE).

Generally, throughout the description set forth herein, the term“plating” is used as exemplary of a number of techniques for overcoatingthe core. It is within the scope of this invention that the core can beovercoated by any suitable technique including, but not limited to:various processes involving deposition of materials out of aqueoussolutions; electrolytic plating; electroless plating; chemical vapordeposition (CVD); physical vapor deposition (PVD); processes causing thedeposition of materials through induced disintegration of liquid orsolid precursors; and the like, all of these techniques for depositingmaterials being generally well known.

Generally, for overcoating the core with a metallic material such asnickel, electrochemical processes are preferred, especially electrolyticplating.

In another embodiment of the invention, the core is an elongate elementof a “hard” material, inherently suitable to functioning as a springelement, and is mounted at one end to a terminal of an electroniccomponent. The core, and at least an adjacent area of the terminal, ispreferably overcoated with a material which will enhance anchoring thecore to the terminal. In this manner, it is not necessary that the corebe well-mounted to the terminal prior to overcoating, and processeswhich are less potentially damaging to the electronic component may beemployed to “tack” the core in place for subsequent overcoating. These“friendly” processes include soldering, gluing, and piercing an end ofthe hard core into a soft portion of the terminal.

Preferably, the core is in the form of a wire. Alternatively, the coreis in the form of a ribbon.

Representative materials, both for the core and for the overcoatings,are disclosed.

In the main hereinafter, techniques involving beginning with arelatively soft (low yield strength) core, which is generally of verysmall dimension (e.g., 3.0 mil or less) are described. Soft materials,such as gold, which attach easily to semiconductor devices, generallylack sufficient resiliency to function as springs. (Such soft, metallicmaterials exhibit primarily plastic, rather than elastic deformation.)Other soft materials which may attach easily to semiconductor devicesand possess appropriate resiliency are often electricallynon-conductive, as in the case of most elastomeric materials. In eithercase, desired structural and electrical characteristics can be impartedto the resulting composite interconnection element by the overcoatingapplied over the core. The resulting composite interconnection elementcan be made very small, yet can exhibit appropriate contact forces.Moreover, a plurality of such composite interconnection elements can bearranged at a fine pitch (e.g., 10 mils), even though they have a length(e.g., 100 mils) which is much greater than the distance to aneighboring composite interconnection element (the distance betweenneighboring interconnection elements being termed “pitch”).

It is within the scope of this invention that composite interconnectionelements can be fabricated on a microminiature scale, for example assmall springs for connectors and sockets, having cross-sectionaldimensions on the order of twenty-five microns (

m), or less. This ability to manufacture reliable interconnection havingdimensions measured in microns, rather than mils, squarely addresses theevolving needs of existing interconnection technology and future areaarray technology.

The composite interconnection elements of the present invention exhibitsuperior electrical characteristics, including electrical conductivity,solderability and low contact resistance. In many cases, deflection ofthe interconnection element in response to applied contact forcesresults in a “wiping” contact, which helps ensure that a reliablecontact is made.

An additional advantage of the present invention is that connectionsmade with the interconnection elements of the present invention arereadily demountable. Soldering, to effect the interconnection to aterminal of an electronic component is optional, but is generally notpreferred at a system level.

According to an aspect of the invention, techniques are described formaking interconnection elements having controlled impedance. Thesetechniques generally involve coating (e.g., electrophoretically) aconductive core or an entire composite interconnection element with adielectric material (insulating layer), and overcoating the dielectricmaterial with an outer layer of a conductive material. By grounding theouter conductive material layer, the resulting interconnection elementcan effectively be shielded, and its impedance can readily becontrolled. (See also FIG. 10K of the PARENT CASE.)

According to an aspect of the invention, interconnection elements can bepre-fabricated as individual units, for later attachment to electroniccomponents. Various techniques for accomplishing this objective are setforth herein. Although not specifically covered in this document, it isdeemed to be relatively straightforward to fabricate a machine that willhandle the mounting of a plurality of individual interconnectionelements to a substrate or, alternatively, suspending a plurality ofindividual interconnection elements in an elastomer, or on a supportsubstrate.

It should clearly be understood that the composite interconnectionelement of the present invention differs dramatically frominterconnection elements of the prior art which have been coated toenhance their electrical conductivity characteristics or to enhancetheir resistance to corrosion.

The overcoating of the present invention is specifically intended tosubstantially enhance anchoring of the interconnection element to aterminal of an electronic component and/or to impart desired resilientcharacteristics to the resulting composite interconnection element.Stresses (contact forces) are directed to portions of theinterconnection elements which are specifically intended to absorb thestresses.

It should also be appreciated that the present invention providesessentially a new technique for making spring structures. Generally, theoperative structure of the resulting spring is a product of plating,rather than of bending and shaping. This opens the door to using a widevariety of materials to establish the spring shape, and a variety of“friendly” processes for attaching the “falsework” of the core toelectronic components. The overcoating functions as a “superstructure”over the “falsework” of the core, both of which terms have their originsin the field of civil engineering.

A distinct advantage of the present invention is that probe elements(resilient contact structures) can be fabricated directly on terminalsof a space transformer substrate component of a probe card assemblywithout requiring additional materials, such as brazing or soldering.

According to an aspect of the invention, any of the resilient contactstructures may be formed as at least two composite interconnectionelements.

A Probe Card Assembly

The aforementioned U.S. patent application Ser. No. 08/554,902 and itscounterpart PCT/US95/14844 disclose a probe card assembly. FIG. 1 ofthis patent application corresponds generally to FIG. 5 of thoseapplications.

FIG. 1 illustrates an embodiment of a probe card assembly 100 whichincludes as its major functional components a probe card 102, aninterposer 104 and a space transformer 106, and which is suitable in usefor making temporary (pressure) electrical connections to asemiconductor wafer 108. In this exploded, cross-sectional view, certainelements of certain components are shown exaggerated, for illustrativeclarity. However, the vertical (as shown) alignment of the variouscomponents is properly indicated by the dashed lines in the figure. Itshould be noted that the interconnection elements (114, 116, 124,discussed in greater detail hereinbelow) are shown in full, rather thanin section.

The probe card component 102 is generally a conventional circuit boardsubstrate having a plurality (two of many shown) of contact areas(terminals) 110 disposed on the top (as viewed) surface thereof.Additional components (not shown) may be mounted to the probe card, suchas active and passive electronic components, connectors, and the like.The terminals 110 on the circuit board may typically be arranged at a100 mil pitch. The probe card 102 is suitably round, having a diameteron the order of 12 inches.

The interposer 104 includes a circuitized substrate 112. In the mannerdescribed hereinabove, a plurality (two of many shown) of resilient(spring) interconnection elements 114 are mounted (by their proximalends) to and extend downward (as viewed) from the bottom (as viewed)surface of the substrate 112, and a corresponding plurality (two of manyshown) of resilient interconnection elements 116 are mounted (by theirproximal ends) to and extend upward (as viewed) from the top (as viewed)surface of the substrate 112. The spring elements 114 are interconnected(not shown) to the spring elements 116 in a conventional manner throughthe substrate 112.

Any of the spring shapes disclosed in any of the aforementionedcommonly-owned patents and patent applications are suitable for use asthe resilient interconnection elements 114 and 116, and they may beimplemented as “composite interconnection elements”. As a generalproposition, the tips (distal ends) of both the lower plurality 114 andof the upper plurality 116 of interconnection elements 114 and 116 areat a pitch which matches that of the terminals 110 of the probe cardcomponent 102, for example 100 mils.

The interconnection elements 114 and 116 are illustrated withexaggerated scale, for illustrative clarity. Typically, theinterconnection elements 114 and 116 would extend to an overall heightof 20-100 mils from respective bottom and top surfaces of the interposersubstrate 112. Generally, the height of the interconnection elements isdictated by the amount of compliance desired.

The space transformer component 106 includes a suitable circuitizedsubstrate 118 such as a multi-layer ceramic substrate having a plurality(two of many shown) of terminals (contact areas, pads) 120 disposed onthe lower (as viewed) surface thereof and a plurality (two of manyshown) of terminals (contact areas, pads) 122 disposed on the upper (asviewed) surface thereof. In this example, the lower plurality of contactpads 120 is disposed at the pitch of the tips of the interconnectionelements 116 (e.g., 100 mils), and the upper plurality of contact pads122 is disposed at a finer (closer) pitch (e.g., 50 mils).

A plurality (two of many shown) of resilient (spring) interconnectionelements 124 (also referred to as “probes” or “probe elements”) aremounted (by their proximal ends) to the terminals 122 and extend upward(as viewed) from the top (as viewed) surface of the space transformersubstrate 118. As illustrated, these probe elements 124 are suitablyarranged so that their tips (distal ends) are spaced at an even finerpitch (e.g., 10 mils) than their proximal ends, thereby augmenting thepitch reduction of the space transformer 106. These resilient contactstructures (interconnection elements) 124 are preferably, but notnecessarily, the aforementioned “composite interconnection elements”.

It is within the scope of the invention that the probe elements (124)can be fabricated on a sacrificial substrate and subsequently mounted tothe terminals (122) of the space transformer component (106), in themanner discussed in the aforementioned commonly-owned U.S. patentapplication Ser. No. 08/788,740 and its counterpart PCT/US96/08107.

As is known, a semiconductor wafer 108 includes a plurality of die sites(not shown) formed by photolithography, deposition, diffusion, and thelike, on its front (lower, as viewed) surface. Typically, these diesites are fabricated to be identical to one another. However, as isknown, flaws in either the wafer itself or in any of the processes towhich the wafer is subjected to form the die sites, can result incertain die sites being non-functional, according to well establishedtest criteria. Often, due to the difficulties attendant probing diesites prior to singulating semiconductor dies from a semiconductorwafer, testing is performed after singulating and packaging thesemiconductor dies. When a flaw is discovered after packaging thesemiconductor die, the net loss is exacerbated by the costs attendant topackaging the die. Semiconductor wafers typically have a diameter of atleast 6 inches, including at least 8 inches.

Each die site typically has a number of contact areas (e.g., bond pads),which may be disposed at any location and in any pattern on the surfaceof the die site. Two (of many) bond pads 126 of a one of the die sitesare illustrated in the figure.

A limited number of techniques are known for testing the die sites,prior to singulating the die sites into individual semiconductor dies. Arepresentative prior art technique involves fabricating a probe cardinsert having a plurality of tungsten “needles” embedded in andextending from a ceramic substrate, each needle making a temporaryconnection to a given one of the bond pads. Such probe card inserts areexpensive and somewhat complex to manufacture, resulting in theirrelatively high cost and in a significant lead time to obtain. Given thewide variety of bond pad arrangements that are possible in semiconductordies, each unique arrangement requires a distinct probe card insert.

The rapidity with which unique semiconductor dies are manufacturedhighlights the urgent need for probe card inserts that are simple andinexpensive to manufacture, with a short turnaround time. The use of aspace transformer (106) having resilient (spring) contact elements (124)mounted thereto and extending therefrom as a probe card insert addressesthis need.

In use, the interposer 104 is disposed on the top (as viewed) surface ofthe probe card 102, and the space transformer 106 is stacked atop (asviewed) the interposer 104 so that the interconnection elements 114 makea reliable pressure contact with the contact terminals 110 of the probecard 102, and so that the interconnection elements 116 make a reliablepressure contact with the contact pads 120 of the space transformer 106.Any suitable mechanism for stacking these components and for ensuringsuch reliable pressure contacts may be employed, a suitable one of whichis described hereinbelow.

The probe card assembly 100 includes the following major components forstacking the interposer 106 and the space transformer 106 onto the probecard 102:

a rear mounting plate 130 made of a rigid material such as stainlesssteel,

an actuator mounting plate 132 made of a rigid material such asstainless steel,

a front mounting plate 134 made of a rigid material such as stainlesssteel,

a plurality (two of many shown, three is preferred) of differentialscrews including an outer differential screw element 136 and an innerdifferential screw element 138,

a mounting ring 140 which is preferably made of a springy material suchas phosphor bronze and which has a pattern of springy tabs (not shown)extending therefrom,

a plurality (two of many shown) of screws 142 for holding the mountingring 138 to the front mounting plate 134 with the space transformer 106captured therebetween,

optionally, a spacer ring 144 disposed between the mounting ring 140 andthe space transformer 106 to accommodate manufacturing tolerances, and

a plurality (two of many shown) of pivot spheres 146 disposed atop (asviewed) the differential screws (e.g., atop the inner differential screwelement 138).

The rear mounting plate 130 is a metal plate or ring (shown as a ring)disposed on the bottom (as shown) surface of the probe card 102. Aplurality (one of many shown) of holes 148 extend through the rearmounting plate.

The actuator mounting plate 132 is a metal plate or ring (shown as aring) disposed on the bottom (as shown) surface of the rear mountingplate 130. A plurality (one of many shown) of holes 110 extend throughthe actuator mounting plate. In use, the actuator mounting plate 132 isaffixed to the rear mounting plate 130 in any suitable manner, such aswith screws (omitted from the figure for illustrative clarity).

The front mounting plate 134 is a rigid, preferably metal ring. In use,the front mounting plate 134 is affixed to the rear mounting plate 130in any suitable manner, such as with screws (omitted from the figure forillustrative clarity) extending through corresponding holes (omittedfrom the figure for illustrative clarity) through the probe card 102,thereby capturing the probe card 102 securely between the front mountingplate 134 and rear mounting plate 130.

The front mounting plate 134 has a flat bottom (as viewed) surfacedisposed against the top (as viewed) surface of the probe card 102. Thefront mounting plate 134 has a large central opening therethrough,defined by an inner edge 112 the thereof, which is sized to permit theplurality of contact terminals 110 of the probe card 102 to residewithin the central opening of the front mounting plate 134, as shown.

As mentioned, the front mounting plate 134 is a ring-like structurehaving a flat bottom (as viewed) surface. The top (as viewed) surface ofthe front mounting plate 134 is stepped, the front mounting plate beingthicker (vertical extent, as viewed) in an outer region thereof than inan inner region thereof. The step, or shoulder is located at theposition of the dashed line (labelled 114), and is sized to permit thespace transformer 106 to clear the outer region of the front mountingplate and rest upon the inner region of the front mounting plate 134(although, as will be seen, the space transformer actually rests uponthe pivot spheres 146).

A plurality (one of many shown) of holes 114 extend into the outerregion of the front mounting plate 134 from the top (as viewed) surfacethereof at least partially through the front mounting plate 134 (theseholes are shown extending only partially through the front mountingplate 134 in the figure) which, as will be seen, receive the ends of acorresponding plurality of the screws 142. To this end, the holes 114are threaded holes. This permits the space transformer 106 to be securedto the front mounting plate by the mounting ring 140, hence urgedagainst the probe card 102.

A plurality (one of many shown) of holes 118 extend completely throughthe thinner, inner region of the front mounting plate 134, and arealigned with a plurality (one of many shown) of corresponding holes 160extending through the probe card 102 which, in turn, are aligned withthe holes 148 in the rear mounting plate and the holes 110 in theactuator mounting plate 138.

The pivot spheres 146 are loosely disposed within the aligned holes 118and 160, at the top (as viewed) end of the inner differential screwelements 138. The outer differential screw elements 136 thread into the(threaded) holes 110 of the actuator mounting plate 132, and the innerdifferential screw elements 138 thread into a threaded bore of the outerdifferential screw elements 136. In this manner, very fine adjustmentscan be made in the positions of the individual pivot spheres 146. Forexample, the outer differential screw elements 136 have an externalthread of 72 threads-per-inch, and the inner differential screw elements138 have an external thread of 80 threads-per inch. By advancing anouter differential screw element 136 one turn into the actuator mountingplate 132 and by holding the corresponding inner differential screwelement 138 stationary (with respect to the actuator mounting plate132), the net change in the position of the corresponding pivot sphere146 will be ‘plus’ 1/72 (0.0139) ‘minus’ 1/80 (0.0125) inches, or 0.0014inches. This permits facile and precise adjustment of the planarity ofthe space transformer 106 vis-a-vis the probe card 102. Hence, thepositions of the tips (top ends, as viewed) of the probes(interconnection elements) 124 can be changed, without changing theorientation of the probe card 102. The importance of this feature, atechnique for performing alignment of the tips of the probes, andalternate mechanisms (means) for adjusting the planarity of the spacetransformer are discussed in greater detail hereinbelow. Evidently, theinterposer 104 ensures that electrical connections are maintainedbetween the space transformer 106 and the probe card 102 throughout thespace transformer's range of adjustment, by virtue of the resilient orcompliant contact structures disposed on the two surfaces of theinterposer.

The probe card assembly 100 is simply assembled by placing theinterposer 104 within the opening 112 of the front mounting plate 134 sothat the tips of the interconnection elements 114 contact the contactterminals 110 of the probe card 102, placing the space transformer 106on top of the interposer 104 so that the tips of the interconnectionelements 116 contact the contact pads 120 of the space transformer 106,optionally placing a spacer 144 atop the space transformer 106, placingthe mounting ring 140 over the spacer 144, and inserting the screws 142through the mounting ring 140 through the spacer 144 and into the holes114 of the front mounting plate 134, and mounting this “subassembly” tothe probe card 102 by inserting screws (one shown partially as 155)through the rear mounting plate 130 and through the probe card 102 intothreaded holes (not shown) in the bottom (as viewed) surface of thefront mounting plate 134. The actuator mounting plate 138 can then beassembled (e.g., with screws, on of which is shown partially as 156) tothe rear mounting plate 130, pivot spheres 160 dropped into the holes150 of the actuator mounting plate 132, and the differential screwelements 136 and 138 inserted into the holes 150 of the actuatormounting plate 132.

In this manner, a probe card assembly is provided having a plurality ofresilient contact structures (124) extending therefrom for makingcontact with a plurality of bond pads (contact areas) on semiconductordies, prior to their singulation from a semiconductor wafer, at a finepitch which is commensurate with today's bond pad spacing. Generally, inuse, the assembly 100 would be employed upside down from what is shownin the figure, with the semiconductor wafer being pushed (by externalmechanisms, not shown) up onto the tips of the resilient contactstructures (124).

As is evident from the figure, the front mounting plate (baseplate) 134determines the position of the interposer 104 vis-a-vis the probe card102. To ensure accurate positioning of the front mounting plate 134vis-a-vis the probe card 102, a plurality of alignment features (omittedfrom the figure for illustrative clarity) such as pins extending fromthe front mounting plate) and holes extending into the probe card 102may be provided.

It is within the scope of this invention that any suitable resilientcontact structures (114, 116, 124) be employed on the interposer (104)and/or the space transformer (106), including tabs (ribbons) of phosphorbronze material or the like brazed or soldered to contact areas on therespective interposer or space transformer.

It is within the scope of this invention that the interposer (104) andthe space transformer (106) can be pre-assembled with one another, suchas with spring clips which are described as element 486 of FIG. 29 ofthe aforementioned copending, commonly-owned PCT/US94/13373, extendingfrom the interposer substrate.

It is within the scope of this invention that the interposer (104) beomitted, and in its stead, a plurality of resilient contact structurescomparable to 114 be mounted directly to the contact pads (120) on thelower surface of the space transformer. However, achieving coplanaritybetween the probe card and the space transformer would be difficult. Aprincipal function of the interposer is to provide compliance to ensuresuch coplanarity.

As illustrated in FIGS. 5A and 5B of the aforementioned U.S. patentapplication Ser. No. 08/554,902 and its counterpart PCT/US95/14844, thetop (as viewed in FIG. 5 therein, or in FIG. 1 herein) can be providedwith a plurality of terminals to which spring contact elements aremounted in a pattern that corresponds a single semiconductor die or to aplurality (e.g., four or more) semiconductor dies which are resident ona semiconductor wafer.

Aligning the Probe Card Assembly

The aforementioned U.S. patent application Ser. No. 08/554,902 and itscounterpart PCT/US95/14844 disclose a technique for aligning thee probecard assembly. FIG. 2 of this patent application corresponds generallyto FIG. 7 of those applications.

FIG. 2 illustrates a technique 200 of aligning a probe card assemblysuch as the probe card assembly 100 of FIG. 1. The view of FIG. 2 ispartially assembled, with the major components in contact with oneanother.

A problem addressed head on by this invention is that it is oftendifficult to align the contact tips of a probe card (or probe cardinsert) with respect to a semiconductor wafer being tested. It isessential that tolerances on the coplanarity of the tips of the probesand the surface of the wafer be held to a minimum, to ensure uniformreliable contact pressure at each the tip 124 a (top ends, as viewed) ofeach probe (i.e, the resilient contact structures 124). As discussedhereinabove, a mechanism (e.g., differential screws 136 and 138) isprovided in the probe card assembly for adjusting the planarity of thetips 124 a of the probes by acting upon the space transformer 106. Inthis figure, the space transformer substrate 106 is illustrated withinternal connection between the top terminals and the bottom terminalsthereof.

Prior to employing the probe card assembly to perform testing on asemiconductor wafer, the alignment of the probe tips is measured and, ifnecessary, adjusted to ensure that the probe tips 124 a will be coplanarwith semiconductor wafers that are subsequently presented to the probecard assembly (i.e., urged against the probe tips).

Generally, a wafer tester (not shown) in which the probe card assemblyis mounted, will have a mechanism (not shown) for conveyingsemiconductor wafers into the region of the probe card assembly andurging the semiconductor wafers against the probe tips 124 a. To thisend, semiconductor wafers are held by a chuck mechanism (not shown). Forpurposes of this discussion, it is assumed that the tester and chuckmechanism are capable of moving wafer-after-wafer into a precise,repeatable location and orientation—the precise location of the waferfunctioning as a “reference plane”.

According to the invention, in order to align the tips 524 a vis-a-visthe expected orientation of a semiconductor wafer, in other wordsvis-a-vis the reference plane, a flat electrically-conductive metalplate 202 is mounted in the tester in lieu of a semiconductor wafer. Theflat metal plate 202 functions as an “ersatz” or “virtual” wafer, forpurposes of aligning the tips 124 a of the probe elements 124.

Each probe element 124 is associated with a one of a plurality ofterminals (not shown) on the probe card 102, a conductive paththerebetween being constituted by a selected one of the probe elements124, an associated selected one of the resilient contact structures 116and an associated selected one of the resilient contact structures 114,and wiring layers (not shown) within the probe card 102. The probe cardterminals may be in the form of surface terminals, terminals of asocket, or the like. A cable 204 connects between the probe card 102 anda computer (tester) 206 which has a display monitor 208. The presentinvention is not limited to using a computing device, nor to a displaymonitor.

In this example, it is assumed that one hundred pressure contacts aresought to be effected between one hundred probe tips 124 a arranged in a10×10 rectangular array and one hundred terminals (e.g., bond pads) of asemiconductor wafer. The present invention is not, however, limited toany particular number of probe tips or any particular layout of bondpads.

The flat metal plate 202 is carried by the chuck (not shown) and urged(advanced, as indicated by the arrow labelled “A”) against the probetips 124 a. This is done in a relatively gradual manner, so that it canbe ascertained whether the probe tips 124 a all contact the flat metalplate in unison (not likely), or whether certain ones of the probe tips124 a are contacted by the flat metal plate 202 prior to remaining onesof the probe tips 124 a. In the illustration, the seventy-one filledcircles (dots) within the area 210 on the monitor 208 indicate thatseventy-one of the probe tips 124 a have been contacted by the flatmetal plate 202 prior to the remaining twenty-nine of the probe tips 124a (illustrated as empty circles) having been contacted by the flat metalplate 202. Based on this visual representation, it is evident that thespace transformer 106 (or, possibly, the metal plate 202) is tilted(canted) to the left (as viewed) downwards (out of the page, as viewed),and the orientation of the space transformer 506 can readily be adjustedby suitable adjustments of the differential screws 136 and 138.

The adjustments necessary to achieve the desired goal of planar,simultaneous contact of all of the tips 124 a with the flat metal plate202, without altering the orientation of the probe card 1502, so thatall of the probe tips 124 a make substantially simultaneous contact withthe flat metal plate 202 are readily calculated, either on-line oroff-line. By making the calculated adjustments, the tips 124 a of theprobes 124 will subsequently make substantially simultaneous contactwith bond pads on semiconductor wafers being tested.

The “go/no-go” (contact/no contact) type of testing discussed in theprevious paragraph is illustrative of a first “order” of alignment thatis facilitated by the probe card assembly of the present invention. Asecond “order” of alignment is readily performed by recording (e.g., inthe computer memory) the sequence (order) in which the probe elementtips contact the metal plate. The first tip to contact the metal plategenerally will generally represent a corner of the space transformerthat is too “high”, and needs to be lowered (e.g., by adjusting thedifferential screws). Likewise, the last tip to contact the metal platewill generally represent a corner of the space transformer that is too“low”, and needs to be heightened (e.g., by adjusting the differentialscrews). It is within the scope of this invention that any suitablealgorithm can be employed to determine the adjustments required to bemade, based on the sequence of tips contacting the metal plate. It isalso within the scope of this invention that a resistance (e.g., toground) between each probe tip 124 a and the flat metal plate 202 can bemeasured and displayed as a numeral, or symbol, or dot color, or thelike, indicative of the measured resistance, rather than merely as afilled circle versus an unfilled circle on the display monitor, althoughsuch is generally not preferred.

It is within the scope of this invention that any suitable mechanism canbe employed for adjusting the orientation of the space transformer106—in other words, planarizing the tips 124 a of probe elements 124.Alternatives to using the differential screws (136, 138) arrangementdiscussed hereinabove would be to use servo mechanisms, piezoelectricdrivers or actuators, magnetostrictive devices, combinations thereof(e.g., for gross and fine adjustments), or the like to accomplish suchplanarizing.

Feedback and Automatic Planarizing

The aforementioned U.S. patent application Ser. No. 08/554,902 and itscounterpart PCT/US95/14844 disclose an alternate (i.e., to thedifferential screws etc.) mechanism for aligning the probe cardassembly. FIG. 3 of this patent application corresponds generally toFIG. 7A of those applications.

FIG. 3 illustrates an automated technique 300 for adjusting the spatialorientation of the space transformer (not shown in this view). In thisexample, an actuator mechanism 302 (labelled “ACT”) is substituted forthe differential screws (136, 138) and operates in response to signalsfrom the computer (e.g., 206). Three such mechanisms 302 can besubstituted for the three pairs of differential screw elements in astraightforward manner. Similar elements in FIG. 3 are labelled withidentical numbers as appear in FIG. 2, and several elements appearing inFIG. 2 are omitted from the view of FIG. 3, for illustrative clarity.

It is also within the scope of this invention that the mechanism(particularly an automated mechanism as illustrated in FIG. 3) forplanarizing the space transformer (106) can be disposed other than asshown in the exemplary embodiments described herein. For example, asuitable mechanism could be located between the top (as viewed) surfaceof the probe card (102) and the front mounting plate (134), orincorporated into the front mounting plate (134). The key feature ofusing any of these mechanisms is the ability to alter the angle(orientation) of the space transformer (e.g., 106) without requiring theorientation of the probe card (102) to be altered.

As used herein, the term “resilient”, as applied to contact structures,implies contact structures (interconnection elements) that exhibitprimarily elastic behavior in response to an applied load (contactforce), and the term “compliant” implies contact structures(interconnection elements) that exhibit both elastic and plasticbehavior in response to an applied load (contact force). As used herein,a “compliant” contact structure is a “resilient” contact structure. Thecomposite interconnection elements of the present invention are aspecial case of either compliant or resilient contact structures.

It is within the scope of the invention, and is generally preferred,that although the interconnection elements 514 and 516 are illustratedin FIG. 5 as single interconnection elements, each illustrated elementis readily implemented as an interconnection structure having two ormore interconnection elements in the manner described hereinabove withrespect to FIG. 3A, to ensure that reliable pressure contacts are madeto the respective contact terminals 510 of the probe card 502 andcontact pads 520 of the space transformer 506.

Mounting the Probe Elements to Silicon

As mentioned hereinabove, the use of a space transformer component (106)in the probe card assembly (100) raises some challenges. For example,when making connections to semiconductor devices to operate them (i.e.,burn-in and/or test), the devices will generate heat and expandaccording to a given coefficient of thermal expansion. Thus, although itis desirable to have a space transformer component that has acoefficient of thermal expansion closely matching that of the silicondevice(s), it would be preferable to have the probe elements (124)mounted to and extending from a substrate that has a coefficient ofthermal expansion which exactly matches that of the silicon devicesbeing operated.

According to the invention, the probe elements (124) are mounted to andextend from a silicon substrate having a coefficient of thermalexpansion which substantially exactly matches that of a wafer (108)being contacted.

Thus, it is within the scope of this invention that the spacetransformer itself (106) is fabricated from a silicon wafer andprovided, if need be, with a rigid backing substrate (not shown). Also,as it turns out, it is easier and more reliable to mount certain typesof free-standing elongate interconnectin elements to a silicon substratethan to a ceramic substrate such as a conventional space transformer.For example, the “composite interconnection elements” discussedhereinbove.

It is, however, preferred to take advantage of a silicon substratecarrying the probe elements to make beneficial modifications to theoverall probe card assembly.

FIGS. 4 and 4A illustrate a probe card insert 400 and probe cardassembly 450 employing the probe card insert 400, respectively.Generally, instead of using a space transformer (106), in thisembodiment the resilient (spring) interconnection (probe) elements 424(compare 124) are mounted to and extend from a first plurality (four ofmany shown in FIG. 4, two of the four shown in FIG. 4A) of terminals 422(compare 122) of an interconnection substrate 418 (compare 118) whichsuch as a piece of or an entire silicon wafer. Also, instead of makingelectrical connections from the probe card 402 (compare 102) to theprobe elements 424 via the intermediary of an interposer (104),electrical connections are made from the probe card 402 to the probeelements 424 via a flexible ribbon-like conductor 404.

The flexible ribbon-like cable 404 has two ends 404 a and 404 b. Thefirst end 404 a is connected to a second plurality (two of many shown inFIG. 4, one of the two shown in FIG. 4A) of terminals 423 disposed onthe interconnection substrate 418. The second end 404 b is connected tothe probe card 402, suitably by a plug 416 at the end 402 b of the cable404 which mates with a corresponding socket 414 which is mounted to theprobe card 402 (or vice-versa).

One having ordinary skill in the art to which this invention most nearlypertains will recognize that each of the terminals 423 are readilyinterconnected via (e.g., within) the substrate 418 with correspondingones of the terminals 422. Traces 426 connect corresponding ones ofterminals 423 and terminals 422. One skilled in the art will recognizethat such traces can be fabricated using any number of well knownsemiconductor manufacturing techniques to form traces that are below, onor above the surface of substrate 418. Compare FIG. 2 and the connectionelements within space transformer 106.

As best viewed in FIG. 4, there are a plurality (two of many shown) ofconductive lines (fingers) 405 extending from the first end 404 a of thecable 404. These 405 are suitably ribbon-like conductors and, in themanner of tape automated bonding (TAB) are readily bonded to therespective terminals 423. Also, the cable 404 is readily made to havecontrolled impedance, being provided with additional conductors (notshown) which are connected to ground.

As illustrated schematically by the pair of two-headed arrows in FIG.4A, there is preferably provided means for controlling the orientation(e.g., planarity) of the interconnection substrate 418 with respect tothe probe card 402. This means is suitably similar to the means forcontrolling orientation described hereinabove with respect to FIG. 1.Taking into account the inherent fragilility of a silicon substrate 418,there is preferably provided a rigid backing (support) member 406 forthe silicon substrate 418. The support member 406 is suitably a plate ofmetal, such as brass or steel, and is sufficiently strong (e.g., stiffand thick) to prevent the silicon substrate 418 from flexing when theprobe card assembly is urged against a WUT (not shown).

As mentioned above, the interconnection substrate 418 is preferablysilicon, to exactly match the coefficient of thermal expansion of theWUT (not shown, see 108 in FIG. 1).

When silicon is used for the interconnection substrate 418, it isreadily provided with active devices, such as field effect transistors(FETs), using conventional semiconductor processing techniques. In thismanner, for example, when simultaneously (i.e., in one touchdown)probing a plurality of memory devices on a WUT and it is determined thata one of the plurality hasa failed (e.g., is shorted out), the “bad”device under test (DUT) can be shut down.

Silicon (418) offers additional advantages over ceramic (418) for thesubstrate to which the probe elements (124, 424) are mounted. Itgenerally has lower series resistance. And it offers more routing (e.g.,from the terminals 423 to the terminals 422) flexibility.

As described hereinabove, the electrical function of the interposer(104) has been “replaced” by the cable 404. However, it will be recalledthat the interposer (104) also worked in concert with the means fororienting the probe card insert, mechanically biasing the substrate ofthe probe card insert away from the probe card. This mechanicalfunction, shown by the pair of two-headed arrows in FIG. 4A, can bereplaced with any suitable means, such as coil springs.

FIG. 4B shows an example of a complete probe card assembly 480 assembledin the manner described hereinabove, utilizing differential screws(compare FIG. 1) and three (two visible) simple coil springs 482 betweenthe top (as viewed) surface of the probe card 402 and the bottom (asviewed) surface of the support member 406. As is evident from thisfigure, the support member 406 can have the same general shape and sizeas the previously-mentioned space transformer 106, in which case severalother elements (i.e., those numbered 1xx) of the previous embodiment 100can be employed in like manner in the embodiment 480.

Although the invention has been illustrated and described in detail inthe drawings and foregoing description, the same is to be considered asillustrative and not restrictive in character—it being understood thatonly preferred embodiments have been shown and described, and that allchanges and modifications that come within the spirit of the inventionare desired to be protected. Undoubtedly, many other “variations” on the“themes” set forth hereinabove will occur to one having ordinary skillin the art to which the present invention most nearly pertains, and suchvariations are intended to be within the scope of the invention, asdisclosed herein. Several of these variations are set forth in theparent case.

For example, prefabricated contact tip structures are readily joined tothe the free ends of the probe elements (424) in the manner describedwith respect to FIGS. 8A-8E of the aforementioned U.S. patentapplication Ser. No. 08/554,902 and its counterpart PCT/US95/14844.

For example, it has been suggested hereinabove that the compositeinterconnection elements of the present invention are but an example ofsuitable resilient contact structures that can be mounted directly toterminals of a space transformer component of a probe card assembly. Forexample, it is within the scope of this invention that needles of aninherently resilient (relatively high yield strength) material, such astungsten, can be coated with a material, such as solder or gold, to makethem solderable, optionally supported in a desired pattern, and joinedsuch as by soldering to the terminals (424) of the interconnectionsubstrate (418).

1. A method of making a probe card assembly for probing a semiconductorwafer, the method comprising: providing a probe card having a pluralityof first contact terminals; providing a semiconductor substrate having aplurality of first substrate terminals and second substrate terminals;providing a plurality of electrical connections connecting selected onesof the plurality of first contact terminals and selected ones of theplurality of first substrate terminals; providing a plurality of probeelements mounted to the second plurality of substrate terminals; andproviding a movable element that controls an orientation of thesubstrate with respect to the probe card.
 2. The method of claim 1wherein providing the substrate comprises providing a substrate made ofsilicon.
 3. The method of claim 1 wherein providing the substratecomprises providing a substrate having approximately the samecoefficient of thermal expansion as the semiconductor wafer.
 4. Themethod of claim 1 wherein providing the substrate comprises providingsecond substrate terminals that are spaced apart from each other at apitch significantly finer than the pitch of the first substrateterminals.
 5. The method of claim 1 wherein providing the substratecomprises providing a substrate that is spaced apart from and securedwithout adhesive to the probe card.
 6. The method of claim 1 whereinproviding the electrical connections comprises providing resilientelectrical connectors.
 7. The method of claim 1 wherein providing theelectrical connections comprises providing composite electricalconnectors.
 8. The method of claim 1 wherein providing the electricalconnections comprises providing tape automated bonds.
 9. The method ofclaim 1 wherein providing the electrical connections comprises providinga ribbon-like cable.
 10. The method of claim 1 wherein providing theelectrical connections comprises providing wirebonds.
 11. The method ofclaim 1 wherein providing the probe elements comprises providingresilient connectors.
 12. The method of claim 1 wherein providing theprobe elements comprises providing composite spring contacts.
 13. Themethod of claim 1 wherein providing the probe elements comprises:mounting to at least one of the second substrate terminals an elongatecore of relatively hard yield strength; overcoating the core withmaterial of relatively low yield strength.
 14. The method of claim 1wherein providing a movable element comprises providing an interposer.15. The method of claim 1 wherein providing a movable element comprisesproviding an interconnection substrate.
 16. The method of claim 1further comprising providing mechanisms for adjusting the orientation ofthe substrate with respect to the probe card.
 17. The method of claim 16wherein providing the mechanisms comprises providing differential screwscoupled to at least one mounting plate.
 18. The method of claim 16wherein providing the mechanisms comprises providing an actuatormechanism coupled to at least one mounting plate.
 19. The method ofclaim 16 providing the mechanisms comprises providing pivot spheres. 20.The method of claim 16 further comprising providing an active deviceintegrated into the semiconductor substrate.
 21. The method of claim 1further comprising providing prefabricated contact tip structuresmounted to the ends of the probe elements.
 22. The method of claim 1further comprising providing a rigid backing for the substrate.
 23. Themethod of claim 1 further providing a biasing element for applying aforce to the substrate that biases the substrate away from the probecard.
 24. The method of claim 23 wherein the biasing element comprises acoil spring.